Structural computational modelling of the tracheo‐bronchial tree of the bottlenose dolphin

Abstract

The trachea of marine mammals is composed by irregular semi‐continuous branching cartilaginous rings, lacks muscular tissue in the dorsal region, and possesses a huge network of venous lacunae in the submucosal layer. Several questions remain open concerning how the tracheal dead space may stand the pressure during prolonged and very deep dives. We investigated the structure of the trachea‐bronchial tree of both the bottlenose dolphin (Tursiops truncatus) and the goat (used for comparison with man), and developed a computational model to simulate the structural deformation of the organ during diving. Biomechanical tests provided reliable data on the stress‐strain relationships for cartilage and connective tissue to be implemented in a computational FE model. Our data showed that in the goat the smooth muscle collapses when external water pressure increases. Contrarily to that, the tracheo‐bronchial tree of the bottlenose dolphin better resists to external pressure due to the stiffer mechanical properties of the cartilage and the peculiar conformation of the cartilaginous rings. Furthermore, the absence of a tracheal muscle increases the robustness of the structure, and the air trapped within contributes to hinder the airways collapse phenomenon.